Under the trademark practice in Japan, a Power of Attorney (PoA) isneeded to be filed to the Japan Patent Office (JPO) for filing a new trademark application.
However, a PoA must be filed when you appoint a new representative against the JPO after filing a trademark application.
Especially, I would like to emphasize that you need to prepare a PoA duly signed by Applicant to respond to Office Action issued for a Japanese trademark application based on an international registration (by the Madrid System) through a new representative domiciled in Japan.
The JPO always requires us to submit anPoA. So please keep it in your mind that you need enough time to prepare the PoA before a deadline for response to Office Action.